Conventional semiconductor light-emitting devices are formed as horizontal devices or vertical devices with an insulating substrate such as sapphire. For example, FIG. 6A illustrates a conventional horizontal semiconductor light-emitting device, and FIG. 6B illustrates a conventional vertical semiconductor light-emitting device.
The horizontal semiconductor light-emitting device includes a buffer layer 2, an n-type nitride semiconductor layer 3, an active layer 4, and a p-type nitride semiconductor layer 5 that are sequentially stacked on a sapphire substrate 1. A p-type electrode 6 is formed on the p-type nitride semiconductor layer 5, and, by removing a partial region of the p-type nitride semiconductor layer 5 and active layer 4 in an etching process, an n-type electrode 7 is formed on an exposed portion of the n-type nitride semiconductor layer 3. However, in the horizontal light-emitting device of FIG. 6A, a light-emitting area is relatively reduced, and a surface leakage current increases, causing the decrease in the emission performance of the horizontal light-emitting device. In addition, since an area through which a current passes is relatively small, a resistance increases, and thus, an operating voltage increases. For this reason, heat is generated, causing the reduction in the service life of the horizontal light-emitting device.
Moreover, in the vertical light-emitting device of FIG. 6B, an operation of forming a p-type nitride semiconductor layer 5 on a substrate is the same as that of the horizontal light-emitting device. An insulating substrate is separated from the light-emitting device before an n-type electrode 7 is formed, and then, the n-type electrode 7 is formed at a bottom of an n-type semiconductor layer 3. In this case, a laser lift-off process is generally used for separation of the insulating substrate. By irradiating a laser beam, which is a strong energy source, on a backside of a transparent sapphire substrate, the laser beam is strongly absorbed in a interface between a buffer layer and the sapphire substrate, and thus, a temperature of 900° C. or more is momentarily produced, whereby a nitride semiconductor in the interface is thereto-chemically dissolved and the sapphire substrate is separated from the vertical light-emitting device. However the laser lift-off process causes the thermal/mechanical deformation of a light-emitting stack structure including an active layer. For example, a mechanical stress occurs between the nitride semiconductor layer and a thick sapphire substrate due to different lattice constants and heat expansion coefficients, and, the vertical nitride semiconductor light-emitting device suffers a mechanical/thermal damage because the vertical nitride semiconductor light-emitting device cannot endure the mechanical stress.
As described above, when a thin film of a stack light-emitting structure is damaged, a high leakage current is caused, and moreover, the chip yield of light-emitting devices is largely reduced, causing the reduction in the entire performance of the light-emitting devices.